1. Field of the Invention
The present invention relates to a flying magnetic head device mounted on a hard disk device or the like, and particularly to a technique suitably used for a magnetic head comprising a slider and a flexure for supporting the slider, both of which are bonded together with a conductive resin film.
2. Description of the Related Art
FIG. 7 is a partial side view showing the structure of a conventional magnetic head device used for a hard disk device. The magnetic head device comprises a slider 1, and a support member 2 for supporting the slider 1.
The slider 1 comprises a ceramic material, or the like. Also, a thin film element 4 is provided on the trailing-side end B of the slider 1. The thin film element 4 comprises a MR head (read head) for detecting a leakage magnetic field from a recording medium such as a hard disk by using magnetoresistance to read a magnetic signal, and an inductive head (write head) comprising a patterned coil.
The support member 2 comprises a load beam 5 and a flexure 6. The load beam 5 comprises a leaf spring material such as stainless steel, and is formed in a structure in which bent portions 5a having rigidity are formed on both sides of the tip portion. A predetermined elastic pressure can be exerted at the base end of the load beam 5 where the bent portions 5a are not formed.
Also, a spherical pivot 7 is formed near the tip end of the load beam 5 so as to project downward as shown in FIG. 7, so that the slider 1 is abutted against the pivot 7 through the flexure 6 described below. The flexure 6 comprises a thin leaf spring made of stainless steel, or the like. The flexure 6 comprises a fixed portion 6a and a tongue piece 6b both of which are connected by a step portion 6c. 
As shown in FIG. 7, the slider 1 is bonded to the bottom of the tongue piece 6b with a resin adhesive 20. The resin adhesive 20 is, for example, a thermosetting epoxy resin. Also, a conductive pattern (not shown in the drawing) is formed in the back side of the tongue piece 6b, and an electrode terminal portion (not shown in the drawing) comprising a thin film led out of the thin film element 4 is provided on the trailing-side end B of the slider 1. Furthermore, a joint 9 is formed at the junction portion between the conductive pattern and the electrode terminal portion by gold (Au) ball bonding. The joint 9 is covered with a reinforcing resin film 10 for protection.
Also, a fillet-like conductive resin film 21 is formed between the leading-side end A of the slider 1 and the tongue piece 6b. The conductive resin film 21 is provided for securing conduction between the slider 1 and the flexure 6, and for dissipating static electricity from the slider 1 to the support member 2. The upper surface of the tongue piece 6b is abutted against the pivot 7 formed on the load beam 5 so that the slider 1 bonded to the bottom of the tongue piece 6b can be freely moved by means of elasticity of the tongue 6b, with the top of the pivot 7 serving as a fulcrum. For the conductive resin film 21, a rigid resin such as a thermosetting epoxy resin or the like is conventionally used as an adhesive (binder).
The slider 1 of the magnetic head device is urged to the disk D by elastic force at the base end of the lead beam 5. The magnetic head device is used for a so-called CSS (Contact Start Stop)-system hard disk device. When the disk D stops, an air bearing surface (ABS) (flying surface) 1a of the slider 1 comes into contact with a recording surface of the disk D due to the elastic force. When the disk D starts, an air flow is led to the space between the slider 1 and the surface of the disk D along the moving direction of the disk D so that the ABS 1a of the slider 1 is subjected to a flying force of the air flow to fly the slider 1 at a short distance δ2 (spacing) from the surface of the disk D.
In a flying state as shown in FIG. 7, the slider 1 is inclined so that the leading side end A is raised higher from the disk D than the trailing-side end B. In this flying state, magnetic signals from the disk D are detected by the RM head of the thin film element 4, or the magnetic signals are written by the inductive head.
The above-described magnetic head device is generally manufactured by a manufacturing process comprising bonding the upper surface of the slider 1 to the lower surface of the tongue piece 6b of the flexure 6, electrically connecting an electrode of the flexure 6 to a pad of the slider 1 through the joint 9 comprising a gold ball, and inspecting the electrical properties of the magnetic head device to select only a good product.
In this case, the electrical properties are inspected under substantially the same condition as in an operation, in which the ABS (flying surface) 1a of the slider 1 comes into contact with the recording surface of the disk D, and then the disk D starts so that the slider 1 flies at a short distance δ2 (spacing) from the surface of the disk D. Therefore, the slider 1 is electrically charged by friction with the disk D to possibly cause a potential difference between the slider 1 and the disk D.
In addition, for example, in a load/unload system head other than the CSS-system hard disk device, a medium is ideally out of contact with a slider, but in fact, the medium is occasionally in contact with the slider (contact during running). Therefore, like in the CSS system, the load/unload system possibly causes a potential difference between the slider and the medium.
In the above-described magnetic head, the conductive resin film 21 is generally thought to secure conduction due to the dielectric breakdown produced between the particles of the conductive filler blended with the resin. Therefore, the resin film 21 does not exhibit conductivity until a voltage over a predetermined threshold value is applied, and thus conduction between the slider 1 and the flexure 6 is not secured until the voltage exceeds the threshold value.
Therefore, when the threshold value is higher than the electrostatic damage limit value at which electrostatic damage (ESD) occurs to a MR element or the like, conduction between the slider 1 and the flexure 6 cannot be secured, and thus an electric charge cannot be dissipated from the conductive resin film 21 to the support member 2 when the slider 1 is electrically charged. There is thus a problem that the thin film element 4 comprising the RM head is possibly electrostatically damaged when the electrically charged slider 1 is in contact with a metal or the like. Particularly, the size (particularly, the thickness) of the MR element tends to decrease more and more, and the withstand voltage also tends to decrease more and more.